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UPSC Civil Services (Mains)

Chemistry optional

  • 2 papers
  • 250 marks each
  • 3 h per paper
  • 5 of 8 questions, Q1 and Q5 compulsory

Paper I covers physical and inorganic chemistry.

UPSC Civil Services (Mains), Chemistry optional · 2024 · Paper I

Q2(b)(i). Bond order of O₂, O₂⁻, O₂²⁻ and O₂⁺

Question

Calculate the bond order for the following: (I) Oxygen, O₂ (II) Superoxide, O₂⁻ (III) Peroxide, O₂²⁻ (IV) Dioxygenyl ion, O₂⁺. Which will have the highest stability?

Answer in brief

Bond order: O₂ = 2, O₂⁻ = 1.5, O₂²⁻ = 1, O₂⁺ = 2.5; the dioxygenyl ion O₂⁺ has the highest bond order, so its bond is the strongest and the most stable.

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Topic notes: molecular orbital theory: LCAO, MO diagrams of N₂, O₂, CO, NO, CN⁻ and HF, bond order and magnetism, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coversbond ordermolecular orbital theorysuperoxideperoxidedioxygenyl ionparamagnetism

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